package j20251019;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket=null;
    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器启动！");
        while(true){
            //1.读取并解析请求
            DatagramPacket requestPacket=new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request=new String(requestPacket.getData(),0, requestPacket.getLength());
            //2.根据请求计算响应
            String response=process(request);
            //3.把响应给客户端
            DatagramPacket responsePacket=new DatagramPacket(response.getBytes(),
                    response.getBytes().length,requestPacket.getSocketAddress());
            socket.send(responsePacket);
            //4.打印一个日志
            System.out.printf("[%s:%d] req:%s resp:%s\n",requestPacket.getAddress().toString(),requestPacket.getPort(),
                    request,response);
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server=new UdpEchoServer(9090);
        server.start();
    }
}
